1. Field of the Invention
The present invention relates generally to a vehicle service technique, and more particularly to a steering angle sensing device for vehicle wheel alignment.
2. Description of the Related Art
Vehicles are major transportation tools in the modern society. Vehicles are widely used in various fields in everyday life. It is very important to people how to use safely vehicles. A vehicle has a chassis structure on which the wheels are mounted. The wheels must be positioned in their true operation positions to ensure safety in driving. Many unexpected factors such as rugged roads, pits and incorrect driving behaviors will all affect the relative position between the wheels and the chassis to cause deflection of the wheels in driving. Under such circumstance, the vehicle will bump, shake and lose its balance when running or cornering at a high speed. After a long period of run under a bumping and shaking state, the parts and tires of the vehicle will abnormally wear to shorten the lifetime of the tires and threaten the safety in driving.
Wheel alignment is an important part of vehicle service for restoring the wheels to their true positions. In general, in wheel alignment, the camber, K.P.I., toe, caster and toe-out on turn of the wheels are calibrated. FIG. 1 shows a conventional detection platform 1 for checking the angle of a wheel. The wheel of the vehicle to be checked is placed on the detection platform 1 and positioned on a turntable 2 for measuring the angle of the wheel. A considerably large room in a garage is needed for arrangement of the detection platform 1. This is unbeneficial to an ordinary garage.
U.S. patent Ser. No. 11/847,319 discloses an apparatus and a method for wheel alignment. In the apparatus, by means of a mounting fixture assembly, a laser device is mounted to the rims of the wheels of motor vehicles. The laser device emits laser beams for detecting the angles of the wheels. Such apparatus is able to provide correct data of angles for a calibration worker. However, the structure of the apparatus is complicated and the cost for the apparatus is relatively high. This is unbeneficial to a small-scale garage.
FIG. 2 shows a simple wheel alignment calibrator 3 in the form of claws. The calibrator 3 is mounted to the rim of a wheel to be detected to provide a calibrated detection point. Then the horizontal and vertical angles of the detection point are measured by means of a conventional measurement tool such as a level or a plumb line to calibrate the angle of the wheel.
The calibrator 3 is able to provide a calibrated detection point for a calibration worker to check the angle of the wheel by means of a conventional level or plumb line. However, in the wheel alignment process, it is necessary to steer the wheel to a specific angle, for example, when calibrating the toe-out on turn of the wheel. In such process, the calibration worker needs a proper tool to check the steering angles of the inner steering wheel and outer steering wheel. The conventional technique fails to provide any steering angle sensing device, which can be used in cooperation with the calibrator.